A Guide to the Selection & Application of Equipment used for the Safety and Conservation of Liquids for Atmospheric and Low Pressure Storage Tanks

1. Storage Tank Safety and Emissions Management
A Guide to the Selection & Application of Equipment used for the Safety and
Conservation of Liquids for Atmospheric and Low Pressure Storage Tanks

2. What happens to tanks when vapor is not properly
managed?

4. Examples of Codes Pertaining to Pressure/Vacuum
Vents & Emergency Relief Vents
API 2000 Venting Atmospheric & Low Pressure Tanks/ISO28300
NFPA 30 Flammable & Combustible Liquids Codes
OSHA 1910 Occupational Safety and Health Act
Examples of Definitions Relating to Pressure/Vacuum
Vents & Emergency Vents
Combustible Liquids, Flammable Liquids Classifications
Low Pressure Storage Tanks – 0.5 to 15 PSIG
Pressure Vessels – Above 15 PSIG

5. Why do tanks need Conservation Vents?
Relieves excess pressure & vacuum created by thermal expansion & contraction
Minimizes costly product evaporation losses during product movement, while protecting
tanks against deformation caused by explosion or implosion
Relieves vapor safely before reaching tank design pressure
Tank is always maintained within design parameters
Reduces EPA regulated emissions
Complies with corporate emissions standards

6. Plan For Reviewing Existing Tanks
• Obtain Design Pressure of the Tank
• Determine the Emergency Relief Pressure Set Point
• Select the Type of Conservation Vent
• Size the Conservation Vent
• Size the Emergency Vent
• Provide Flame Arresters

7. Select the Vent/Valve Type
WEIGHT LOADED PILOT OPERATED SPRING LOADED
0.865”W.C. - 4 PSI - 2”W.C. - 15 PSI 1 - 15 PSI
(CLOSED SHOWN) (OPEN SHOWN)

8. Characteristics of Weight Loaded Venting Devices
• Set pressure is defined by total pallet weight, including loading weights
• Does not flow at set pressure or set vacuum
• As tank pressure approaches set pressure, the pallet begins to fluctuate on the seat
• At set pressure, the pallet is weightless
• The vent begins to flow at overpressure
• Flow characteristic is defined by the flow curve associated with the style and size of the
vent
• Set pressures are limited to the practical amount of weight loaded onto the pallet

9. Control Technology for Weight Loaded Vents
Flat Pallet, 1 scfh leakage Air Groove 1 scfh leakage
= Pallet, = @ 90% of set
Soft Seat @ 80% of set
pressure Soft Seat pressure

10. Characteristics of Spring Loaded Vents
Spring Tension controls the set pressure
As tank pressure approaches set pressure, the pallet begins to fluctuate
Pallet lifts at set pressure
Flow characteristic is defined by the associated flow curve of the size and style of vent

11. Characteristics of Pilot-Operated Vents
Spring Tension controls the set pressure
As tank pressure approaches set pressure, the pallet begins to fluctuate
Set pressure is achieved by applying pilot tank pressure to diaphragm chamber
Vent is “bubble tight” up to set pressure
Flow is achieved at set pressure with “pop-action” pilot
Full flow is achieved at 10% over-pressure
Adjustable flow at set pressure with “modulating-action” pilot
Adjustable blow-down
Test in place capabilities
Pallet lifts at set pressure
Flow characteristic is defined by the associated flow curve of the size and style of vent

12. Set Points
API RULES S&J RECOMMENDATIONS
ERV set point = Tank design ERV set point = 80% of tank design
pressure pressure
PRV set point = less than ERV PRV set point = 80% of ERV set point (64%
of tank design pressure)
WHY 80% SET POINT FOR PRV?
This is 25% overpressure for vent
…which optimizes its efficiency

13. API 2000 Formula for Determining Normal Venting
Requirements - Liquid Movement and Thermal

14. Conservation Vents/Valves
S & J 94020 S & J 94040
Conservation Vent Spring Loaded
Conservation Vent
S & J 94110
Vacuum Vent S & J 94130 S&J 94640
Pressure Vent Pilot Operated Relief Valve

15. API 2521: Allowable Leakage
% Set Point
API 2521: 5 scfh @ 75% Set Point for 8” size or larger
1/2 scfh @ 75% Set Point for 6” size or smaller
Air Groove Pallet: 1 scfh @ 90% Set Point for all sizes
Expanda-Seal: 1/2 scfh @ 95% Set Point for all sizes

16. EXPANDA-SEAL
TEST DATA FOR LEAKAGE RATE OF WEIGHT LOADED EXPANDA-SEAL
PALLET SET AT 1 OZ/IN2
% OF VITON TEFLON
SET POINT LEAKAGE RATE LEAKAGE RATE
95% 0.5 (SCFH) 0.5 (SCFH)
90% < 0.5 (SCFH) < 0.5 (SCFH)
75% < 0.5 (SCFH) < 0.5 (SCFH)
50% < 0.5 (SCFH) < 0.5 (SCFH)

17. EXPANDA-SEAL
To reduce emissions, Shand & Jurs designed and patented a high performance gasket, called Expanda-Seal™, which
has reduced emissions and odors for the past fifteen years in every process environment imaginable. This innovative
design actually uses the internal vessel pressure to create a tighter seal the closer the pressure gets to the set point.
VALVE OPEN
When pressure inside the tank is As the pressure approaches the set point, the When the pressure in the tank is at
below the set point, the deflated gasket, shown here in yellow, inflates and or above set point, the valve lifts
diaphragm rests on the seat ring in a wraps around the mating seat to achieve this to relieve the overpressure.
typical manner, as with any normal unique sealing effect.
valve, retaining internal pressure.
Click on the Diagram below to see
the Operation of Expanda-Seal
Expanda-Seal Pallet
<1/2 scfh leakage @ 95%
of set pressure

18. EXPANDA-SEAL Advantages
LESS ODOR
LESS VOC EMISSIONS
RECLOSES AFTER RELIEF
0.5 SCFH AT 95% OF SET POINT
LOWER FIRST COST BENEFITS
VALUABLE PRODUCT RETAINED
SIMPLE WEIGHT LOADED PALLET DESIGN

19. Conservation Vent with Limit Switch

20. Conservation Vent with Visual Indicator
99060 Duracator

21. Quantify Emissions
1. Calculate pallet lift
2. Send information to DCS

22. Open vs. Closed Venting
Open Conservation Vent Closed Conservation Vent

23. Effect of Back-Pressure on Set Pressure
Back pressures and negative pressures in vent manifolds affect vent set pressure
Set pressures are reduced by constant or variable negative pressures
Leakage of valuable inert gas may occur
Valve chatter may occur, causing pre-mature wear of pallets and seats
Pre-mature wear will create additional leakage

24. Why do tanks need an Emergency Vent?
Provides emergency pressure relief in case of a storage tank fire or abnormal pressure
conditions
As storage tank contents rise in temperature, emergency vent allows for required venting
capacity, preventing tank rupture
Prevents tank from rupturing due to overpressure
Operates when relief capacity exceeds normal vent capacity
Available in pressure/vacuum and pressure only configurations
Larger sizes permit access into tank

28. This is what you don’t want to ever happen

29. Emergency Vents
SET POINTS
API RULES S&J RECOMMENDATIONS
ERV set point = Tank design ERV set point = 80% of tank design
pressure pressure

30. 3 Types of Emergency Vents
WEIGHT LOADED
SPRING LOADED
MAGNETIC

31. Weight Loaded Emergency Vent

32. Spring Loaded Emergency Vent

33. Magnetic Emergency Vent

34. Formula for Determining Emergency Venting
Requirements per API 2000

35. Emergency Vent and Manhole Covers
S & J 94200/94201 S & J 94210
Emergency Vent Emergency Vent
and Manhole and Manhole Cover
Cover
S & J 94221 S & J 94510
Emergency Vent Emergency
and Manhole “Magnavent”
Cover
S & J 94520 S&J 94250
Emergency Pressure Vent Spring Loaded
and Manhole Cover Emergency Vent

36. EXPANDA-SEAL
To reduce emissions, Shand & Jurs designed and patented a high performance gasket, called Expanda-Seal™, which
has reduced emissions and odors for the past five years in every process environment imaginable. This innovative
design actually uses the internal vessel pressure to create a tighter seal the closer the pressure gets to the set point.
VALVE OPEN
When pressure inside the tank is As the pressure approaches the set point, the When the pressure in the tank is at
below the set point, the deflated gasket, shown here in yellow, inflates and or above set point, the valve lifts
diaphragm rests on the seat ring in a wraps around the mating seat to achieve this to relieve the overpressure.
typical manner, as with any normal unique sealing effect.
valve, retaining internal pressure.
Click on the Diagram below to see
the Operation of Expanda-Seal
Expanda-Seal Pallet
<1/2 scfh leakage @ 95%
of set pressure

37. What is Gas Blanketing?
• Usually a low pressure blanket
• Maintains protective gaseous environment
• Fills tank vapor space with inert gas

38. Gas Blanketing is used to:
• Usually a low pressure blanket
• Prevent emission of toxic vapors
• Minimize loss of valuable products through evaporation
• Prevent product contamination
• Prevent emission of flammable hydrocarbon vapors
• Prevent formation of flammable vapor to air mixture in tanks
• Minimize internal tank corrosion from acids or oxygenation
• Maintains protective gaseous environment
• Fills tank vapor space with inert gas

39. Methods

40. 94210
94270
94020

41. Sizing Blanket Requirements

42. Adding Blanketing Valve Failure to Vent Flow

43. Set Points for Vents and Emergency Vents with
Blanketing
• Set Point for P/V Vent Pressure =
• Blanket Valve Set Point + 3” WC
• Set Point for Emergency Vent =
• P/V Vent Pressure Setting + 2” WC Min